THE ORGANIC ELEMENTS. 25 



eluded, from observations on substitution in plants, and supported by 

 chemical analogy, that there is a transition from sugar into dextrin, from 

 dextrin into starch, amyloid, cellulose, and vegetable jelly, from wax into 

 sugar, from sugar and starch into wax, from starch into fixed oils, and 

 from the fixed oils into sugar and dextrin. In these changes the same 

 or very similar compound bodies, through merely taking up or depositing 

 water or oxygen, constitute the very foundations of vegetable change, 

 the formation and metamorphosis of the elementary organs, and thus 

 form an essential part of the so-called life. Any one who would wish to 

 study vegetable physiology, and every botanist must do this who attaches 

 importance to science, will not neglect a thorough investigation of the 

 subjects embraced in the sections of this work concerning Organic 

 Chemistry. 



SECTION II. 



ON THE REMAINING ORGANIC SUBSTANCES FORMED UNDER THE 

 INFLUENCE OF VEGETATION. 



12. Amongst the numerous principles present in plants are 

 some which appear to stand in a close relation with the general 

 process of vegetation, and which are generally present : these are, 

 1. Chlorophyll ; 2. the other colouring matters of plants ; 3. 

 Malic, Citric, and Tartaric Acids ; 4. Alkaloids ; 5. Tannin ; 6. 

 Viscin and Caoutchouc ; 7. Humus. 



1. Chlorophyll (Blatt-griin, fcecula viridis, Chromule, Phytochlor, 

 green vegetable wax). If any green part of a plant is bruised and sub- 

 mitted to the action of alcohol, a green tincture is formed. If this be 

 evaporated to dryness under the exhausted receiver of an air-pump, a 

 green fatty mass is left, which forms soaps with the alkalies. If this is 

 dissolved in ether and mixed with water, and the ether evaporated, small 

 greasy globules are obtained, which appear of a green colour by reflected 

 light, and of a Burgundy-red by transmitted light. Similar globules are 

 separated from the alcoholic solution by a freezing temperature. If the 

 alcoholic tincture is mixed with water and the alcohol evaporated by 

 heat, a part of the fatty substance is thrown down, the water itself is 

 coloured of a brown-yellow, and has a characteristic smell like that of 

 black tea. This is what is commonly called chlorophyll. When treated 

 with sulphuric acid it is either not changed or becomes carbonised ; it is 

 not dissolved or coloured blue, as is erroneously stated by Marquart.* 

 It is soluble in volatile and fixed oils. 



This substance is found in all plants growing in the light, with the 

 exception of some of the alga?, fungi, and lichens, and the true parasites, 

 covering either conformably the cell-walls or the spiral bands, as in 

 Spirogyra, or the granular contents of the cells which are composed of 

 starch or the other similar bodies, j Only in the last sense can we speak 

 of granules of chlorophyll, as granules consisting entirely of chlorophyll 

 are unknown. It is never found in the form of vesicles. J 



* See Hugo Mohl on the Winter Colouring of Leaves, Tubingen, 1837. 



f Hugo, Researches upon the Anatomical Relations of Chlorophyll. Tubingen, 

 1837. 



\ Smith (Elem. Thil. Bot. ed. 2.) does not state liow lie satisfied himself of chloro- 

 phyll vesicles. 



